A device and system for controlling load currents are disclosed and, more particularly, a device and system for controlling currents to a load from plural parallel power sources having hot swap capabilities.
“Hot swapping” refers to the ability of an electronic system or network of electronic systems to continue operating without interrupting the delivery of power to the system or network of systems after modules or components of the system or network, e.g., a hard drive, a power supply, a CD-ROM drive, and the like, are removed and replaced. Typically, during a hot swapping insertion, current to a load is ramped ON (or, alternatively, during extraction, current to a load is ramped OFF) in a controlled, linear manner to prevent disturbances on the power supply feed. This feature allows modules or components to be inserted into or extracted from a powered system without having to shut off power. Hot swap devices often include a current control function that prevents current to a load from exceeding a programmed maximum level. Thus, hot swapping reduces system down time and improves system availability.
High availability (“HA”) systems are particularly desirable, especially in telecommunications. For example, the Advanced Telecom Computer Architecture (“ATCA”) provides a common, high availability hardware platform for telecommunications systems. The standardized ATCA hardware platform includes a plurality of interconnected circuit boards and a chassis portion, or card shelf. By convention, each card shelf provides 14 or 16 slots for cards.
A scaled-down and less expensive version of the ATCA is the MicroTCA. MicroTCA supports smaller scale applications and is less powerful than ACTA but, otherwise, is similar in many respects. A major difference between the MicroTCA and the ATCA is that the MicroTCA does not include a carrier board.
Advantageously, both the ATCA and the MicroTCA are compatible with Advanced Mezzanine Cards (“AMCs”). AMCs are designed to be installed and to operate in a MicroTCA chassis or, alternatively, in an ATCA carrier board. AMCs are fully-managed intelligent cards that require hotswap protection. Hotswap circuitry for AMCs, however, is not on the AMC boards but, rather, is part of the MicroTCA power module or, alternatively, is part of the ATCA carrier board.
To improve the reliability of HA systems, redundant, parallel power sources are desirable. However, with plural power sources in parallel, the maximum current available to the load (“load current”) is the sum of the output currents of each of the plural power sources. If all power sources are delivering current, the current level, typically, is unacceptably large. As a result, conventional power sources are not coupled in parallel in conjunction with ATCAs, MicroTCAs, and/or AMCs.
Therefore, it would be desirable to provide a system for controlling current levels from plural parallel power sources to a load and a device for the same. It would also be desirable to provide a device for use with plural parallel power sources that controls current rather than load shares.